Some of the so-called healthy snack foods and packaged goods you're tossing into your grocery cart each week may be filled with "extras" that can, in the long term, put your health at risk.

Everyone knows to keep an eye out for calories, fat, and carbs when they're browsing the supermarket aisles. But are you paying attention to the little-known, flavor-enhancing, often lab-generated chemicals that manufacturers pump into food to cut costs and keep you hooked? Just because it isn't making you fat doesn't mean it's not rotting you inside and out.

If you look out for only nine ingredients the next time you go shopping for food, make them these. And as a rule of thumb, aim for whole foods—minimally processed stuff that will get you the important nutrients without any extra processed crap.

1. PARTIALLY HYDROGENATED OIL

This nemesis of heart health is the primary source of trans fat. Manufacturers like it because it reduces costs, increases shelf life and stabilizes flavor, but it's a lose-lose for consumers. Trans fats are twice as difficult for the body to dissolve as saturated fats, and because they boost bad (LDL) cholesterol and have been shown to decrease good (HDL) cholesterol, they're active agents of heart disease, diabetes, nutritional deficiencies and cellular deterioration. Note: Products that contain partially hydrogenated oils, but have less than 0.5g of trans fat per serving can carry a “trans-fat free” label. Also keep in mind that “fully hydrogenated oil” does not contain trans fats.

2. HIGH-FRUCTOSE CORN SYRUP

Though chemically similar to table sugar (sucrose), this cheaper alternative is a highly processed form of glucose converted into fructose—the type of sugar ordinarily found in fruit. There are many cases to be made against HFCS: some studies have shown that it inhibits leptin—the hormone responsible for telling your brain that you're full. And while some people will argue that it's essentually just sugar, one thing is certain: Too much sugar will harm bodily processes in countless ways, including increasing risk for diabetes, obesity and other metabolic disorders.

3. MSG

MSG goes by many names: monosodium glutamate, maltodextrin, sodium caseinate, autolyzed yeast, autolyzed vegetable protein, hydrolyzed vegetable protein, yeast extract, and even citric acid. Ultimately, more than 40 forms of this processed additive can be found in grocery store aisles. MSG is also a chemoinducer of obesity, type II diabetes and metabolic syndrome.

4. BHA (BUTYLATED HYDROXYANISOLE) and BHT (BUTYLATED HYDROXYTOLUENE)

Antioxidants are normally good, right? Not in this case. BHA and BHT are antioxidant preservatives used in cereals, potato chips and chewing gum to keep them from going rancid. The Department of Health and Human Services pegged them as known carcinogens, but, mysteriously, the FDA allows them. The additives negatively impact sleep and appetite, and have been associated with liver and kidney damage, hair loss, behavioral problems, and cancer.

5. SODIUM NITRATE AND SODIUM NITRITE

These additives are used as colorants, and to preserve the shelf life of meats like hot dogs, bacon and sausage. That all sounds OK until you note that they mix with stomach acids to form nitrosamines, potent cancer-causing cells associated with oral, stomach, brain, esophageal and bladder cancers. Noticeable side effects include dizziness, headaches, nausea and vomiting. Want quick deli meats without the drawbacks? Stick to choices like Natural Choice Hormel, which is additive-free.

6. PROPYL GALLATE

This next antioxidant preservative is used by food manufacturers to prevent fats and oils from spoiling, and is often used in conjunction with BHA and BHT. Its claim to infamy: It might cause cancer, though the evidence to support this isn't conclusive. Watch out for it in vegetable oil, potato sticks, chicken soup base, meat products, chewing gum and cosmetic products.

7. SODIUM BENZOATE AND BENZOIC ACID

These additives are used in some fruit juices, carbonated drinks, and pickles to stymie the growth of microorganisms in acidic foods. Though they’re naturally occurring and generally affect only people with allergies, there's another problem: When sodium benzoate is used in beverages also containing ascorbic acid (aka vitamin C), the substances can form small amounts of benzene, a chemical that causes leukemia and other cancers. Though the benzene amounts are small, you should generally avoid it, especially in acid-containing foods and beverages.

8. POTASSIUM BROMATE

Wonder bread may not be so wonderful. Potassium bromate—an additive used in breads and rolls to increase their volume and produce a fine crumb structure—has been banned by every other industrialized country other than the U.S. and Japan. For the most part, it breaks down into inert bromide, but any leftover bromate that hangs around in the body has been shown to cause cancer in lab animals. Potassium bromate may also be used to produce some types of malted barley, too, so double-check the labels of your favorite breads and crackers for potassium bromate in disguise. The good news: There are plenty of other baked goods that eschew potassium bromate in favor of safer alternatives.

9. FOOD COLORINGS

Although some foods are colored with natural substances like beta-carotene and carmine, some 17.8 million pounds of food dyes (many of which are petroleum-derived) are consumed in America, according to a 2005 survey by the Feingold Association. The good news is that 17 of 24 synthetic dyes have been banned from use in American foods. So what’s wrong with a little color? Red #3, used in candy, baked goods and desserts, has demonstrated chromosomal damage and thyroid tumors. Red #40, found in drinks, desserts, candy and pet food, has spurred lymph tumors in lab testing. Yellow #5 (aka tartrazine) and #6 may cause thyroid and kidney tumors, lymphocytic lymphomas, and chromosomal damage.

Bottom Line: They’re used in pet food, beverages, baked goods, desserts, candy and sausage. Your best bet is to opt for foods that use natural dyes like beta-carotene or annatto, or those that are dye-free. To have a game plan before you hit the grocery store, get the facts on popular brand-name products at labelwatch.com.